Fuel injection apparatus

ABSTRACT

In a fuel injection apparatus in which an air sensor deflected as a function of the intake air quantities maintains the air-tofuel ratio at a constant value and wherein the return force affecting the air sensor and opposing the deflecting force of the air flow is derived from pressurized liquid, the pressure of said liquid is varied by altering, in response to at least one engine variable, such as the oxygen content of the exhaust gas, the energizing current of a movable coil armature. The latter, together with a stationary permanent magnet, is incorporated in a pressure control valve that affects the pressure of said liquid.

O United States Patent [1 1 1111 3,796,200

Knapp Mar. 12, 1974 FUEL INJECTION APPARATUS 3,713,430 1/1973 Knapp 123/139 Aw [76] inventor Heinrich Knapp Hummelbergweg 3,728,993 4/1973 Eckert 123/139 AW 3,739,758 6/1973 K 123/139 AW 24, 725 Le0nberg-S1lberberg,

Primary Examiner-Manuel A. Antonakas [22] Filed: Jan. 10, 1973 Assistant Examiner-R. H. Lazarus 1 App o 3 Attorney, Agent, or FirmEdwin E. Greigg [57] ABSTRACT [30] Foreign Application Priority Data In a fuel injection apparatus in which an air sensor de- Jan. 26, 1972 Germany 2203507 flected as a function of the intake air quantities maintains the air-to-fuel ratio at a constant value and [52] US CL. 123/119 R, 123/139 AW, 123/32 AE, wherein the return force affecting the air sensor and 60/285, 60/276 opposing the deflecting force of the air flow is derived [51] Int. Cl. F02m 69/00 from Pressurized liquid, the Pressure of Said liquid is [58] Field of Se h 123/32 AB, 32 EA, 119R varied by altering, in response to at least one engine 123/ 139 AW variable, such as the oxygen content of the exhaust gas, the energizing current of a movable coil armature. [56] References Cit d The latter, together with a stationary permanent mag- UNITED STATES PATENTS net, is incorporated in a pressure control valve that af- 3,680,535 8/1972 Eckert 123/139 AW fects the pressure of Sand 3,543,739 12/1970 Mennesson 1 4. 123/32 EA 4 Claims, 2 Drawing Figures 3,710,769 l/l973 Knapp 123/139 AW PATENTEBIAMZBN 3'796'200 sum 1 or 2 Fig.1

FUEL INJECTION APPARATUS BACKGROUND OF THE INVENTION This invention relates to a fuel injection apparatus serving a spark plug-ignited internal combustion engine which operates on fuel continuously injected into the suction pipe containing an arbitrarily operable butterfly valve. The apparatus is of the type which includes an air sensor situated in the suction pipe spaced from the butterfly valve and defiectable by and in proportion to the throughgoing air quantities against a normally constant return force. The latter, however, is variable in response to engine variables. The air sensor actuates the movable member of a fuel metering valve disposed in the fuel line for metering fuel quantities which are at a desired ratio with the air quantities. The alteration of the return force is effected by an electromagnet, the magnetic field strength of which and thus the spring bias of a pressure control valve is variable, for example, as a function of the oxygen content in the exhaust gas by means of oxygen sonde. The aforenoted pressure control valve, in turn, controls the liquid pressure which serves as the return force associated with the air sensor. A fuel injection apparatus of this type is disclosed in US. patent application to Knapp, Ser. No. 269,175, filed July 5, 1972 and owned by the same assignee as the present application.

The exhaust gas of internal combustion engines contains, among others, carbon monoxide, oxides of nitrogen and uncombusted or only partially combusted hydrocarbons which contribute to a substantial extent to air pollution. For converting the noxious components in the exhaust gas into harmless compounds, the exhaust gas is, above its reaction temperature, passed through a catalyzer. For such a procedure it is a requirement that the exhaust gas has a composition which makes possible a practically complete conver sion into harmless compounds. Thus, the ratio of air to the fuel has to be approximately stoichiometrical which corresponds to an air ratio 7\ that is close to 1.

In the aforeoutlined fuel injection apparatus the pressurized liquid that serves as the return force for the air sensor may be affected as a function of the oxygen content in the exhaust gas of the internal combustion engine by causing the armature of the electromagnet to exert a force on a diaphragm which forms the movable member of the pressure control valve. The magnetic made is maintained at a small value by using nickelcontaining iron. The residual hysteresis of the soft iron,

however, introduces even in case of a very good material, a hysteresis in the signal utilization. This occurrence may lead to deviations from the optimal point or to oscillations in the regulation if the deviations are not immediately picked up and compensated.

OBJECT AND SUMMARY OF THE INVENTION parent from the ensuing detailed specification of a preferred, although exemplary embodiment taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional, partially schematic view of a fuel injection apparatus incorporating the invention and FIG. 2 is a diagram of a circuit for controlling the energizing current of the pressure control valve as a function of the oxygen concentration in the exhaust gas.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the fuel injection apparatus illustrated in FIG. 1, the intake air flows in the direction of the arrow into a suction tube portion 1 and then into a conical suction tube portion 3 in which there is disposed an air sensor 2. Thereafter the intake air flows through a connecting hose 4 into a suction tube portion 5 in which there is disposed an arbitrarily operable butterfly valve 6. Therefrom the intake air flows to one or more cylinders (not shown) of an internal combustion engine (also not shown). The air sensor 2 is formed as a plate disposed normal to the direction of air flow and is movable by and as an approximately linear function of the air quantities flowing through the suction tube. In case ofa constant return force exerted on the air sensor 2 and in case of a constant pressure prevailing upstream of the air sensor 2, the pressure between the air sensor 2 and the butterfly valve 6 will also be constant.

The air sensor 2 controls directly a quantity distributor and metering valve 7. For transmitting the motion of the air sensor 2 to the fuel metering valve 7 there is provided a lever 8 which carries the air sensor plate 2 and which is pivotally mounted in a frictionless member at ajoint 9. The lever 8 has an integral lug 10 which actuates the movable valve member 11 of the fuel metering valve 7. The movable valve member 11 is designed as a control plunger. One radial face 12 of the control plunger 11 is exposed to pressurized liquid which serves as the return force for the air sensor 2.

Fuel supply is effected by means of a fuel pump 16 which is driven by an electromotor l5 and which draws fuel from a fuel tank 17 and forces it to the metering valve 7 through a conduit 18. From the conduit 18 there extends a conduit 19 containing a pressure limiting valve 20.

From the conduit 18 the fuel is admitted into a channel 21 in the housing of the fuel quantity distributor and metering valve 7. The channel 21 leads to an annular groove 22 of the control plunger 11 and further, through separate branches, to a plurality of chambers 23 (only one shown). Each chamber 23 is bounded by a diaphragm 24, so that one side of a diaphragm 24 is exposed to the fuel pressure prevailing in chambers 23. Dependent upon the position of the control plunger 11, the annular groove 22 overlaps to a greater or lesser extent control slots 25 which lead through individual channels 26 to separate chambers 27 (only one shown) which are separated from the associated chambers 23 by the diaphragm 24. From the chambers 27 the fuel is admitted through channels 28 (only one shown) to the individual fuel injection valves (not shown) which are situated in the suction tube in the vicinity of the associated engine cylinder. The diaphragm 24 serves as the movable member of a flat seat valve which, when the fuel injection apparatus is not operating, is maintained in an open position by a spring 29. The diaphragm boxes each formed of a chamber 23 and a chamber 27 and each containing a flat seat valve, ensure that independently from the extent of overlap between the annular groove 22 and the control slot 25, that is, independently from the fuel quantities flowing to the fuel injection valves, the pressure drop across the fuel metering components 22, 25 is maintained substantially at a constant value. In this manner it is ensured that the extent of displacement of the control plunger 11 is proportionate to the metered fuel quantities.

The pressurized liquid which serves as the constant return force affecting the control plunger 11 is fuel. For this purpose, from the conduit 18 there extends a conduit 32 which opens into a channel 35 which, in turn, is in communication with a pressure chamber 33. The control plunger 11 projects into the pressure chamber 33 with its radial face 12. In the conduit 32 there is situated a throttle 34 which separates the fuel supply circuit 18 of the quantity distributor and fuel metering valve 7 from the control pressure circuit 32, 35. The fuel is admitted through the channel 35 to a pressure control valve 36 and therefrom the fuel is adapted to flow back into the fuel tank 17 in a depressurized manner through a return conduit 37. The pressure control valve 36 is formed as a flat seat valve having a metallic diaphragm 24 as its movable valve member. The diaphragm 24 clamped between a base body 38 and a housing 39 defines together with a stationary valve seat 40 arranged in the base body 38 the flow passage section of the pressure control valve in its open position. A small motion of the diaphragm 24 suffices to open the full, annular flow passage section of the valve, whereby the throughgoing fuel may return in a depressurized manner into the fuel tank 17 through the return conduit 37. The diaphragm 24 is loaded through supports 43, 44 and an interconnecting member 45 by a leaf spring 46 which is formed as a spider and which is biased in such a manner that it exerts its force in the closing direction of the valve.

With the leaf spring 46 there is fixedly connected a movable coil armature 47 which includes a wire coil 48. About the movable coil armature 47 there is situated an annular soft iron core 49 which is joined in an axial direction by an annular permanent magnet 50. To the latter there is attached a soft iron plate 51 having a core 52 which projects into the movable coil armature 47.

The aforedescribed fuel injection apparatus operates as follows:

When the internal combustion engine is running, the pump 16 driven by the electromotor draws fuel from the fuel tank 17 and drives it through the conduit 18 to the quantity distributor and metering valve 7. Simultaneously, the internal combustion engine draws intake air through the suction pipe. The air flow causes the air sensor 2 to execute a certain excursion from its position of rest. As a function of the excursion of the air sensor 2 the control plunger 11 is displaced by the lever 8 and, as a result, a larger flow passage section will be opened at the control slots 25. The direct connection between the air sensor 2 and the control plunger 11 ensures a constant ratio of air quantities to the metered fuel quantities.

For maintaining the fuel-air mixture at a richer or leaner level as a function of the range in which the internal combustion engine momentarily operates, a change of the return force (which is constant by itself) of the air sensor 2 is required as a function of engine variables. This is effected by either sensing the engine variables electronically or after conversion into electric magnitudes they are changed by an electric control apparatus to corresponding current intensities that vary the magnetic field strength of the coil 48. In this manner the movable coil armature 47 is opposed to a greater or lesser extent to the bias of the leaf spring 46. Since the pressure control valve requires only a minimum excursion of its movable valve member for the control of pressure of the return force, the magnetic force, that is, the control current, may be converted directly into pressure. By virtue of suspending the movable coil armature 47 by means of the leaf spring 46 and by designing the pressure control valve as a flat seat valve, the mechanical operation of the latter is entirely without friction and is, by virtue of using a coil armature-type magnetic system, entirely hysteresis free.

As illustrated in FIG. 1 it is expedient to integrate the pressure control valve 36 with the quantity distributor and metering valve 7, whereby the diaphragm 24 is used for both valves as the movable valve member. It is, nevertheless, feasible to design the pressure control valve entirely separately from the quantity distributor and metering valve 7.

The fuel injection apparatus may, by virtue of an appropriate configuration of the conical suction tube portion 3 designed for a predetermined air ratio A. Preferably, the conical suction tube portion is designed for an air ratio A that is approximately 1.05, while the readjustment of the air ratio to A l is effected by means of an oxygen sonde illustrated in FIG. 2. Thus, the fuel-air mixture is enriched from the lean side.

Turning now to a detailed description of the A adjusting circuit illustrated in FIG. 2, there is shown a wall 59 which separates a chamber 61 through which flows the exhaust gas of the internal combustion engine, from a chamber 62 which communicates with the ambient atmosphere. In the wall 59 there is arranged the oxygen sonde 60 in such a manner that a contacting material 64, provided on an ion-conductive solid electrolyte 63 communicates at one side 64 with the exhaust gas of the internal combustion engine, that is, with the chamber 61 and on its other side 65 with the ambient atmosphere, that is, with the chamber 62. The oxygen ion-conducting solid electrolyte 63 may be stabilized zirconium dioxide, thorium dioxide or mullite (the latter is a fire and high temperature-resistant material having the formula 3Al O 2SiO2). The members 64 and 65 are porous, gas-pervious foil-like components which are applied in a very thin layer and which may be formed of platinum of high temperature-resistant hard electric material such as tungsten carbide or high temperature-resistant, electrically conductive oxides of the type of Fe O Between the foils 64 and 65 there is generated a certain potential difference which is a function of the oxygen content of the exhaust gases. This potential difference is compared with a reference potential which, in turn, is obtained by means of an appropriately high-resistance (ohmic) voltage divider formed of two resistances 66 and 67. The aforenoted comparison of potentials is effected in an operational amplifier 68. The output voltage of the latter is applied to the base of an emitter follower transistor 69 and thus determines the energizing current of the wire coil 48 of the pressure control valve 36. In order to ensure that at full load the internal combustion engine delivers the highest torque, the butterfly valve 6, shortly before reaching its fully open position, operates a switch 70 having in series a resistance 71. Thus, upon actuation of the switch 70 there is obtained a higher energizing current for the wire coil 48. A higher energizing current flowing through the wire coil 48 means a decrease of the return force exerted on the control plunger 11 and thus an increase of the metered fuel quantities. The

What is claimed is:

1. In a fuel injection apparatus serving a spark plugignited internal combustion engine operating on fuel continuously injected into the engine suction pipe containing an arbitrarily operable butterfly valve, said apparatus being of the type that has (a) a fuel metering valve including a movable valve member disposed in the fuel line of the engine, (b) an air sensor disposed in said suction pipe spaced from said butterfly valve, said air sensor being deflectable by and as a function of the air quantities flowing through said suction pipe, (0) means for exerting areturn force on said air sensor, said last-named means including pressurized liquid, (11) means for connecting said air sensor to said movable valve member to displace the latter for metering fuel quantities that are proportionate to the intake air quantities flowing through said suction pipe, said metered fuel quantities also being a function of the magnitude of said return force, (e) a pressure control valve connected with said means for exerting a return force on said air sensor, said pressure control valve having a movable valve member loaded by spring means for controlling the pressure of said pressurized liquid, (f) an electromagnet incorporated in said pressure control valve for varying, as a function of the intensity of its energizing current, the load on the movable valve member of said pressure control valve, said energizing current characterizing at least one engine variable, the improvement comprising A. a movable coil armature connected at least indirectly to said spring means,

B. a permanent magnet disposed adjacent said movable coil armature and being magnetically linked therewith and C. means for passing an energizing current through said movable coil armature as a function of at least one engine variable. 2. An improvement as defined in claim 1, including A. a diaphragm constituting said movable valve member of said pressure control valve and B. a coupling member operatively connecting said movable coil armature to said diaphragm.

4. An improvement as defined in claim 3, wherein said coupling member is constituted by a leaf spring. 

1. In a fuel injection apparatus serving a spark plug-ignited internal combustion engine operating on fuel continuously injected into the engine suction pipe containing an arbitrarily operable butterfly valve, said apparatus being of the type that has (a) a fuel metering valve including a movable valve member disposed in the fuel line of the engine, (b) an air sensor disposed in said suction pipe spaced from said butterfly valve, said air sensor being deflectable by and as a function of the air quantities flowing through said suction pipe, (c) means for exerting a return force on said air sensor, said last-named means including pressurized liquid, (d) means for connecting said air sensor to said movable valve member to displace the latter for metering fuel quantities that are proportionate to the intake air quantities flowing through said suction pipe, said metered fuel quantities also being a function of the magnitude of said return force, (e) a pressure control valve connected with said means for exerting a return force on said air sensor, said pressure control valve having a movable valve member loaded by spring means for controlling the pressure of said pressurized liquid, (f) an electromagnet incorporated in said pressure control valve for varying, as a function of the intensity of its energizing current, the load on the movable valve member of said pressure control valve, said energizing current characterizing at least one engine variable, the improvement comprising A. a movable coil armature connected at least indirectly to said spring means, B. a permanent magnet disposed adjacent said movable coil armature and being magnetically linked therewith and C. means for passing an energizing current through said movable coil armature as a function of at least one engine variable.
 2. An improvement as defined in claim 1, including A. housing means surrounding said movable coil armature, B. a leaf spring affixed to said housing and C. means securing said movable coil armature to said leaf spring for a friction-free suspension of said movable coil armature from said leaf spring.
 3. An improvement as defined in claim 1, including A. a diaphragm constituting said movable valve member of said pressure control valve and B. a coupling member operatively connecting said movable coil armature to said diaphragm.
 4. An improvement as defined in claim 3, wherein said coupling member is constituted by a leaf spring. 